STRUCTURAL TIMBERS

TIMBER PRESERVATION

Timber preservation has been available for many years and was generally provided in the form of CCA, LOSP and Borate treatments of timber. These are three very different forms of timber treatments that provide applications for varying situation usage.

HistoryOLYMPUS DIGITAL CAMERA

Timber preservation has been practised since early times when pitch derived from plant resins (known as ‘rosin’) or the soaking of timbers in olive oil was used in ancient Greek and Roman civilisations. The plant resins (or pitch as they were referred to) were generally derived from pines and conifers and were later to become replaced by bitumen as derived from petroleum products. In China, the extensive use of Tung oil was recorded with this oil being produced from the pressings of the seed in the nut from the Tung tree. Other oils that were used in timber preservation included linseed, rapeseed and sunflower oils. In fact, timber preservation has been around nearly as long as the use of wood in various applications.

CCA TIMBER PRESERVATION TREATMENT

CCA was generally applied as a plant treatment whereby copper, chromium and arsenate were applied by pressure in units designed to impregnate the timber against the effects of insects, rot and fungus. CCA is most commonly used in timber manufactured for outdoor use as decking, fencing, landscaping, telephone poles, stumps on pole homes and outdoor furniture.Some of its uses in recent times have been curtailed by the Australian Pesticide and Veterinary Medicines Authority (APVMA) because of issues associated with the toxicity of the ingredients of CCA. Many countries throughout the world have either banned or restricted the use of CCA for a range of reasons that relate to health and environmental concerns pertaining to manufacture, use and end-of-use disposal issues. People who treat the timber or handle the timber once it has been treated are exposed to health risks where sufficient precautions have not been undertaken and the Australian Workers Union has banned some of the traditional CCA timber construction methods. CCA treated timber leaching copper, chromium and arsenate into the environment has been the subject of several academic studies with special consideration provided to the impact of heavy metals leaching into soil and groundwater supplies. The incineration of CCA treated timber releases toxins into the air which has been the case where bushfires have occurred, and this also has been the subject of academic studies. Incineration of CCA treated timber is banned in some Australian States for these reasons. In Australia, CCA treated timber is generally disposed of in specially designated landfill areas, although this is a practise that has been banned in Europe where CCA treated timber has been categorised as a hazardous waste. Unfortunately, most replacement timber treatment technologies also have issues relating to toxicity and carcinogenic effects on humans similar to those experienced by CCA treatments. Ammoniacal Copper Quaternary (ACQ), Copper Azole and Creosote are timber treatments that have issues that relate to either health and safety concerns with toxicity, and/or carcinogenic effects on humans. Boron Solutions is currently exploring a unique new methodology for the disposal of “end-of-use” CCA treated timber to provide a means whereby we are able to facilitate an environmentally friendly solution to the current problem. This is an important issue highlighted by the exponential growth of future management requirements for the safe disposal of CCA treated timber at end-of-life.

LOSP (LIGHT ORGANIC SOLVENT PRESERVATIVE)

LOSP has become available as an alternate means of treating timber in situations where timbers are undercover or in an exposed above-ground situation (H2 & H3). In an exposed situation, these treatments will generally need to be sealed with an appropriate paint or sealant product. These treatments provide minimal protection as ‘envelope’ treatments that achieve some minor penetration into the outer surface of the timber. Problems are surfacing relative to handling issues that pertain to the use of solvents that carry the active constituents into the timber. This has caused extensive review to be undertaken as to the health and handling risks associated with these treatments. The active constituents will generally include either a synthetic pyrethroid (such as permethrin, deltamethrin, cypermethrin or bifenthrin), copper napthenate, tributyl tin oxide (TBTO) or tributyl tin naphthenate (TBTN). There is no requirement for heartwood to be treated by this process and there are obvious concerns where the ‘envelope’ is broken when saw-cuts and variations to dimensions are effected on-site during the construction process. It should be noted that LOSP is not designed to treat heartwood and only treats the sapwood of timber, and solvents used in the process can react on metal fixings and fastenings causing them to degrade. In recent times, cheaper means of application have been used to apply synthetic pyrethroids with linseed oil and rapeseed oil that have reduced costs and also created a reduced envelope penetration of the treated construction timbers. Oils, and linseed oil in particular, can often become a food source for fungi and generally require to be administered with an appropriate fungicide to prevent subsequent timber rot and decay.

BORATE (BORON) TREATMENTS

IMG_20140415_211922 Borate treatments have been used for many years with their recognition as a benign eco-friendly form of timber preservation.The treatment of timber with borates has been associated in the past with leaching problems because where it is used in as an uncovered treatment (exposed to the elements) it would leach over a period of time. However, in a covered above-ground situation, the borates will reside in the timber for the lifetime use of the timber in service and in an exposed above-ground situation where the timber was protected with an appropriate sealant; the treatment would continue to operate as long as it remained sealed against exposure. Borate treatments are not new and have been extensively used to preserve telephone poles, bridges and fenceposts (H3, H4 & H5 use), whereby the borates are used as a “diffusible” timber preservative. What this means is that boron stick (similar to chalk sticks) are placed in drill holes in the timber and are replenished on a regular basis as they continue to travel in the timber on the moisture lines therein providing ongoing protection with regular servicing. Recent developments have resulted in borate treatments that can provide full-infusion of construction timbers with both sapwood and heartwood being able to be treated. Borates represent the longest continually registered insecticides in the world and provide fungal and insect protection of timber unrivalled by other recognised timber preservation technologies. The other beneficial aspect of borate infusion in timber is that it provides fire retardancy and smoke suppression that other treatments are unable to impart. In fact, solvent use in timber preservation treatments can actually assist the spread of fire. Boron is a natural element that is mined throughout countries such as the USA, Turkey, China, Argentina, Chile and other countries to have a host of industrial uses. Many environmental groups are pushing for the greater use of borates in timber preservation to offset the use of the chemical timber preservation products that are being reviewed because of health issues in handling treated timbers as well as toxicity and ‘end-of-use’ disposal issues that beset the world’s environment.

THE TIMBER PRESERVATION STANDARD

The Australian Standard for Timber Preservation is discussed as AS 1604 “Specification for Preservative Treatment” and relates to six Hazard Classes pertaining to the use of the timber and the conditions to which it is subjected. The Hazard Classes are discussed as H1 – H6 and a brief discussion to familiarise you with the various classes is provided as follows

H1 – The timber must be inside and above-ground so as to be completely protected from weather, well ventilated and protected from termites and is primarily concerned with lyctid borer activity in susceptible framing, joinery, flooring and furniture.

H2 – The timber is again protected from moisture and the treatment deals with the effects of both borers and termites with the timber being in an above-ground, covered situation.

H3 – The timber is in an above-ground, outside and exposed situation where it is required to deal with the effects of moisture, moderate decay, borers and termites. The timber needs to be protected with suitable sealants against leaching and prescribes situations concerning external weatherboard, decking, fascia and pergola timbers (No ground contact).

H4 – The timber is in an outside, in-ground and in an exposed situation where the timber is exposed to extensive wetting, leaching, severe decay as well as borers and termites. This references timber usage as fence-posts, in-ground pergolas, greenhouses and landscaping timbers.

The timber is in an outside, in-ground situation in contact with fresh water thereby requiring a higher degree of protection from the effects of leaching and extreme wetting as well as borers and termites. This references timber usage as retaining walls, piling, house stumps and building poles. The timber is subject to prolonged exposure to marine (sea) water immersion and requires protection against decay and marine wood borers. This references timber used in sea water including jetties, landing steps, boat hulls, etc. It should be noted that Australian Standards are often developed by industry operatives who become part of the Standard’s committee that creates the Standard. This has been previously noted by the Productivity Commission, and the reasoning behind these practises is to create a Standard that specifies systems and treatments of the manufacturer. The ACCC has further confirmed this to be the case. The Timber Treatment Standard and the Termite Management Standards are excellent examples of the pecuniary interests of manufacturers and system providers having sway in the creation of Standards that imbed their technologies whilst limiting access to competing technologies through dictates in the Standards.